Apparatus for aerating a particulate material

ABSTRACT

An apparatus for forcing airflow through (i.e., aerating) a particulate material consists of a planar bearing surface and a ventilation conduit underlying the planar bearing surface. A plurality of delivery conduits extend between the ventilation conduit and the planar bearing surface with a mouth of the delivery conduits being near the planar bearing surface. A grate, defining a plurality of openings, covers the mouth of each delivery conduit. Each grate has a top surface substantially parallel to the planar bearing surface and positioned at or no more than a select distance below the planar bearing surface. This select distance is close enough to the planar bearing surface to prevent the accumulation of particulate material over the grate as the particulate material is scraped from the planar bearing surface with an implement having a linear edge abutting the planar bearing surface.

BACKGROUND OF THE INVENTION

[0001] 1. Technical Field

[0002] The present invention is directed toward aeration of particulatematerial, and more particularly toward an apparatus for aeratingparticulate material such as compost.

[0003] 2. Background Art

[0004] Increasing waste production and decreasing capacity for wastedisposal has led to exploration of alternatives for conventionallandfilling of waste. The ability to compost organic waste to reduce thevolume of waste and produce a usable byproduct has led to expansion ofthe composting industry.

[0005] One known method and apparatus for composting is disclosed inAllen, U.S. Pat. No. 6,099,613 (the “Cedar Grove patent”), the contentsof which are incorporated herein in their entirety. The Cedar Grovepatent is directed to a composting system and apparatus using pavementas a bearing surface for piles of particulate composting material. Aplurality of ventilation conduits underlie the pavement surface and aplurality of delivery conduits extend between the ventilation conduitand the pavement surface to provide aeration to particulate compostingmaterial deployed on the pavement surface. The Cedar Grove patentrecognizes the need to provide a grate covering the delivery conduits.In order to protect the grate from equipment used to move compostingmaterial on the pavement surface, is teaches recessing the grates belowthe pavement surface about 2-5 inches. It further teaches providingopenings in the grates sized to prevent rocks and other debris fromentering the delivery conduits.

[0006] In practice, debris gets packed into the recess overlying thegrates and significantly inhibits the flow of air through the grates,thus diminishing efficient composting. In order to handle denser, wetterfeed stocks, the Cedar Grove system requires disposable tees to beinstalled loosely over each recessed air grate. The cost of the tees aswell as the time and effort required to place and replace the tees inthe recess increases the cost of this composting system.

[0007] Finn, U.S. Pat. No. 5,758,482, is directed to an air floorgrating system for use in curing compost. Finn teaches a system havingelongate air channels that are covered with elongate grates having a topsurface at about the level of a bearing surface of the compost curingsystem. The grates of the Finn system feature air passages which areintended not to plug under traffic by rubber-tired vehicles used formanipulating the compost. More particularly, the openings of the Finnsystem features a narrow slot at the top surface which tapers to a wideropening at the bottom of the grate. The design is intended to ensurethat compost entering the slot does not plug the opening, but fallsthrough the opening and into the trench below to provide a self-cleaningunit.

[0008] The system of Finn relies on easy access to the underlying airchannels to provide cleaning and removal of material falling into theair channels through the grates. Another problem with the system of Finninvolves accidental displacement of the grates. This allows a largevolume of material to enter the air channels and disrupts a uniform airflow. Also, the small slits described in Finn (0.05-0.063 inch at thesurface) cannot accommodate high moisture conditions that causehydraulic swelling of smaller organic matter particles. In addition, thelinear system of Finn is subject to non-uniform air flow from one end ofan air channel to another in the event of displacement of a grate orvarying back pressures caused by non-uniform distribution of compostingmaterial over the grates.

[0009] The present invention is intended to overcome one or more of theproblems discussed above.

SUMMARY OF THE INVENTION

[0010] An apparatus for forcing airflow through (i.e., aerating) aparticulate material consists of a planar bearing surface and aventilation conduit underlying the planar bearing surface. A pluralityof delivery conduits extend between the ventilation conduit and theplanar bearing surface with a mouth of the delivery conduits being nearthe planar bearing surface. A grate, defining a plurality of openings,covers the mouth of each delivery conduit. Each grate has a top surfacesubstantially parallel to the planar bearing surface and positioned ator no more than a select distance below the planar bearing surface. Thisselect distance is close enough to the planar bearing surface to preventthe accumulation of particulate material over the grate as theparticulate material is scraped from the planar bearing surface with animplement having a linear edge abutting the planar bearing surface. Theventilation conduit preferably underlies the planar bearing surface at adepth sufficient to prevent damage to the ventilation conduit as theimplement having a linear edge abutting the planar bearing surface movesover the planar bearing surface. The grate openings have a length and awidth. The width may be sized so that no more than 50% (by weight) ofthe particulate material would have a particle size smaller than thatmeasured by a sieve equal to the width of the openings and larger than a0.08 inch sieve. Each grate preferably includes at least one keeperprojecting from a bottom surface of the grate which is received withinan inner diameter of an associated delivery conduit to prevent lateralmovement of the grate. A pressurized air source is preferably providedin fluid communication with the ventilation conduit. The source mayprovide a positive or negative air pressure. The ventilation conduit ispreferably essentially linear and the plurality of delivery conduits arespaced relative to adjacent delivery conduits along the ventilationconduit at distances that decrease as the delivery conduits are furtherspaced from the pressurized air source. This distance is chosen so thateach delivery conduit delivers air at essentially the same rate with theparticulate matter overlying the planar bearing surface at an operativedepth. Each grate preferably has a weight sufficient to maintain it inplace as the particulate material is scraped from the planar bearingsurface with an implement having a linear edge abutting the planarbearing surface. The weight is preferably also sufficient so that thegrate remains in place when positive air pressure is applied to thedelivery conduits.

[0011] Another aspect of the invention is a composting apparatus forcomposting organic particulate material. The composting apparatusincludes a pavement slab having a planar bearing surface. A ventilationconduit underlies the pavement slab. A plurality of delivery conduitsextend between the ventilation conduit and the planar bearing surface ofthe pavement with the mouth of the delivery conduits being near theplanar bearing surface. A grate defining a plurality of openings coversthe mouth of each delivery conduit. Each grate has a top surfacesubstantially parallel to the planar bearing surface and positioned atno more than a select distance from the planar bearing surface. Theselect distance is close enough to the planar bearing surface to preventthe accumulation of particulate material over the grate as theparticulate material is scraped from the planar bearing surface with animplement having a linear edge abutting the planar bearing surface. Eachgrating opening has a length and a width. The width is sized so that nomore than 50% (by weight) of the particulate material would have aparticle size smaller than that measured by a sieve equal to the widthof the openings and larger than a 0.08″ sieve.

[0012] The apparatus for aerating particulate material in accordancewith the present invention eliminates the recess over the air grate ofthe Cedar Grove system and, therefore, enables a more uniform air flowthan obtainable using the Cedar Grove system. The system also eliminatesthe expense and difficulty associated with using tees in the recessesnecessitated by the Cedar Grove system in order to maintain uniform airflow. The grate openings are sized to allow material to fall through thegrate rather than obstructing the grate. This material may then beremoved by vacuuming the conduits or applying a back pressure to theconduits. The system of the present invention provides grates which aresecurely positioned over the delivery conduits, thus eliminatingdisplacement of the grates which could allow uncontrolled entry ofmaterial into the delivery conduits, producing blockage and uneven airflow. The grates are also durable enough to sustain the load ofequipment used in moving and treating the compost.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a perspective view of an apparatus for aeratingparticulate material in accordance with the present invention;

[0014]FIG. 2 is a perspective view of the air conveyance system of theapparatus for aerating particulate material of FIG. 1 with the pavementand underlying soil removed;

[0015]FIG. 3 is a cross-section of a delivery conduit and grate of theapparatus for aerating particulate material of FIG. 1; and

[0016]FIG. 4 is a plan view of a grate for aerating particulate materialin accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0017] An apparatus for aerating particulate material 10 of the presentinvention is illustrated in FIG. 1. The apparatus consists of a pavementslab 12 having a number of rows of vent holes 14 for aeratingparticulate material 16 deployed on the pavement slab 12. A pressurizedair source 18 is in operative association with an air conveyance system26 which will be discussed below with respect to FIG. 2. The pressurizedair source 18 is configured either to provide air under positivepressure or negative pressure (i.e., to create a vacuum at the ventholes 14). The pavement slab 12 and the vent holes 14 are intended tobear material moving equipment 20. The material moving equipment 20 mayinclude a plow or front end loader 22 or other implement having a linearedge 24 abutting a planar bearing surface 38 (shown in FIG. 3) of thepavement slab 12 to allow for manipulation and loading of theparticulate material 16.

[0018] In a preferred embodiment, the particulate material 16 consistsof relatively uniformly sized particles. Representative particles couldbe materials for compost, biofilter (or soil filter) grains, soil fordecontamination and any other particulate matter that it would be usefulor desirable to provide a flow of air through.

[0019] An air conveyance system 26 for the apparatus for aeratingparticulate material 10 of the present invention is shown in FIG. 2 withthe pavement slab 12 and underlying soil removed for sake of clarity.The air conveyance system 26 consists of a plenum conduit 28 which is influid communication with the pressurized air source 18 shown in FIG. 1.A plurality of ventilation conduits 30 extend from the plenum conduit 28under the pavement slab 12, preferably within a plane parallel to theplanar bearing surface 38, shown in FIG. 3, of the pavement slab 12.Each ventilation conduit 30 has a number of delivery conduits 32, eachof which has a mouth 34 near the planar bearing surface 38 of thepavement slab 12. As seen in FIG. 2, the delivery conduits 32 are spacedcloser to each other toward a distal end of the ventilation conduits 30,or away from the pressurized air source 18. This differential spacing isintended to deliver air at essentially the same rate to the mouth 34 ofeach delivery conduit 32 so as to provide a relatively even distributionof air to a bed of particulate material 16 deployed on the pavement slab12 at an operative depth. “Operative depth” means a depth suitable forventilation by the apparatus for aerating particulate material 10.

[0020]FIG. 3 shows in detail the interface between the air conveyancesystem 26 and the pavement slab 12. The ventilation conduit 30 liesunder the pavement slab 12 and a layer of soil 36 at a depth sufficientto protect the ventilation conduit 30 from damage as material movingequipment 20 moves over the pavement slab 12. The delivery conduit 32can be seen to extend to the ventilation conduit 30 so that its mouth 34is near the planar bearing surface 38 of the pavement slab 12. A shallowrecess 40 in the planar bearing surface 38 of the pavement slab 12 isdimensioned to receive a grate 42 which covers the mouth 34 of thedelivery conduit 32. The shallow recess 40 is of a diameter slightlygreater than the outer diameter of the delivery conduit 32 to define anannular shoulder 43 on which a circumferential edge of the grate 42rests. The shallow recess 40 is configured so that a top surface 44 ofthe grate 42 is substantially parallel to the planar bearing surface 38.As used herein, “substantially parallel to” means that no portion of thetop surface 44 of the grate 42 within the shallow recess 40 extendsabove the planar bearing surface 38 if the top surface 44 of the grate42 is not truly parallel to the planar bearing surface 38. With thegrate 42 deployed in the shallow recess 40, the top surface 44 of thegrate 42 is “coplanar” with the planar bearing surface 38 or, asillustrated in FIG. 3, slightly below the planar bearing surface 38. Thedistance d between the planar bearing surface 38 and the top surface 44of the grate 42 is preferably small enough that particulate material 16will not fill the shallow recess 40 above the top surface 44 of thegrate 42 when the planar bearing surface 38 is scraped with an implementhaving a linear edge 24 abutting the planar bearing surface 38, such asthe material moving equipment 20 illustrated in FIG. 1. Preferably, thedistance d is no greater than {fraction (1/8)} inch for most particulatematerial.

[0021] The grate 42 has a plurality of keepers 46 which extend in anaxial direction beyond a back surface of the grate 42. The keepers 46are radially spaced to engage an inner diameter of the delivery conduit32 so as to prevent lateral displacement of the grate 42 within themouth 34. The grate 42 may be made of any of the following materials:steel alloy, aluminum, fiberglass reinforced plastic (FRP) or rubber.Preferably, the grate 42 will be made of cast steel or aluminum alloyfor greater bearing strength, as material moving equipment 20manipulating the particulate material 16 may weigh 80,000 pounds ormore. Use of a metal such as steel or an aluminum alloy also makes thegrate 42 heavy enough that it will remain in place over the mouth 34 ofthe delivery conduit 32 while particulate material 16 is being handledon the planar bearing surface 38. The use of a dense material for thegrate 42 also allows it to stay in place under positive air pressurerepresented by arrow 48 or negative air pressure represented by thearrow 50. In a preferred embodiment, an o-ring 52 made of a dense orclosed-cell foam lies between the bottom of the grate 42 and the annularshoulder 43.

[0022]FIG. 4 shows the top surface 44 of the grate 42 in a plan view.The grate 42 has a number of openings 56 having a length and a width x.The width x is selected to be large enough so that particulate material16 being aerated will not clog the opening 56, but instead small amountswill be able to fall through the openings 56 into the delivery conduit32. Preferably, the width x is sized so that no more than 50% (byweight) of the particulate material 16 being aerated would have aparticle size smaller than that measured by a sieve equal to the widthof the opening and larger than a 0.08 inch sieve. Alternatively, thewidth x is sized so that no more than 60% (by volume) would have aparticle size smaller than that measured by a sieve equal to the widthof the opening. When cleaning of the air conveyance system 26 to removeparticles which have fallen therein is required, the grate 42 may beremoved manually and debris blown out the mouth 34 of the deliveryconduits 32 by a positive pressure applied to the air conveyance system26, or a negative pressure can be applied to the air conveyance system26 to suck out particulate debris.

[0023] In a preferred embodiment, the apparatus for aerating particulatematerial 10 is used for composting organic particulate material orforcing air through a biofilter. In this embodiment, the openings 56preferably have a width x of greater than 0.25 inch and may be in arange of 0.25-0.75 inch, depending upon the size of the particulateorganic material being composted. Other uses for the device could be asa biofilter, an air distribution surface, bioremediation aerationsurface for ventilating biopiles, drying manure and sludges, and dryingcrops. The width of the openings x would vary in each application asnecessary to aerate the size particles being treated.

1. An apparatus for aerating a particulate material, the apparatuscomprising: a planar bearing surface; a ventilation conduit underlyingthe planar bearing surface; a plurality of delivery conduits extendingbetween the ventilation conduit and the planar bearing surface with amouth of the delivery conduits being near the planar bearing surface;and a grate defining a plurality of openings covering the mouth of eachdelivery conduit, each grate having a top surface substantially parallelto the planar bearing surface and positioned at or no more than a selectdistance below the planar bearing surface, the select distance beingclose enough to the planar bearing surface to prevent the accumulationof particulate material over the grate as the particulate material isscraped from the bearing surface with an implement having a linear edgeabutting the planar bearing surface.
 2. The apparatus of claim 1 whereinthe ventilation conduit underlies the planar bearing surface at a depthsufficient to prevent damage to the ventilation conduit as the implementhaving a linear edge abutting the planar bearing surface moves over theplanar bearing surface.
 3. The apparatus of claim 1 wherein the grateopenings have a length and a width, the width being sized so that nomore than 50% (by weight) of the particulate material would have aparticle size smaller than that measured by a sieve equal to the widthof the openings and larger than a 0.08 inch sieve.
 4. The apparatus ofclaim 1 wherein the grate includes at least one keeper projectingopposite the top surface, the keeper being received within an innerdiameter of the delivery conduit to prevent lateral movement of thegrate.
 5. The apparatus of claim 1 further including a pressurized airsource in fluid communication with the ventilation conduit, theventilation conduit being essentially linear and the plurality ofdelivery conduits being spaced relative to adjacent delivery conduitsalong the ventilation conduit at distances that decrease as the deliveryconduits are further spaced from the pressurized air source, thedistances being chosen so that each delivery conduit delivers air atessentially the same rate with the particulate material overlying thebearing surface at an operative depth.
 6. The apparatus of claim 1wherein the grate has a weight sufficient to maintain it in place as theparticulate material is scraped from the planar bearing surface with animplement having a linear edge abutting the planar bearing surface. 7.The apparatus of claim 6 wherein the grate is made of steel or aluminumalloy.
 8. The apparatus of claim 1 further comprising an o-ring sealbetween each grate and the mouth of the delivery conduits.
 10. Ancomposting apparatus for composting organic particulate material, thecomposting apparatus comprising: a pavement slab having a planar bearingsurface; a ventilation conduit underlying the pavement slab; a pluralityof delivery conduits extending between the ventilation conduit and theplanar bearing surface of the pavement with a mouth of the deliveryconduits being near the planar bearing surface; and a grate defining aplurality of openings covering the mouth of each delivery conduit, eachgrate having a top surface substantially parallel to the planar bearingsurface and positioned at or no more than a select distance below theplanar bearing surface, the select distance being close enough to theplanar bearing surface to prevent the accumulation of particulatematerial over the grate as the particulate material is scraped from thebearing surface with an implement having a linear edge abutting theplanar bearing surface, each grating opening having a length and awidth, the width being sized so that no more than 50% (by weight) of theparticulate material would have a particle size smaller than thatmeasured by a sieve equal to the width of the openings and larger than a0.08 inch sieve.
 11. The apparatus of claim 10 wherein the ventilationconduit underlies the pavement at a depth sufficient to prevent damageto the ventilation conduit the implement having a linear edge abuttingthe planar bearing surface moves over the planar surface.
 12. Theapparatus of claim 10 wherein the grate includes at least one keeperprojecting opposite the top surface received within an inner diameter ofthe delivery conduit to prevent lateral movement of the grate.
 13. Theapparatus of claim 10 further including a source of pressurized air influid communication with the ventilation conduit, the ventilationconduit being essentially linear and the plurality of delivery conduitsbeing spaced along the ventilation conduit at distances that decrease asthe delivery conduits are further from the source of pressurized air,the distances being chosen so that each delivery conduit delivers air atessentially the same rate with the particulate material overlying thebearing surface at an operative depth.